Bruce Lilly <blilly(_at_)erols(_dot_)com> writes:
RFC 2822 permits (as did 822) a quoted string which
consists solely of a pair of DQUOTE characters. It's
not clear what the semantics of that are or ought to be.
Likewise, a domain literal can consist solely of the
square brackets.
The combination of the two means that the following is
syntactically valid as an angle-addr or msg-id:
<""@[]>
Perhaps these empty contructs could be relegated to obs-
status in the next revision, with the generate syntax
changed to use 1* instead of * for the content within a
quoted-string and domain-literal.
qmail makes use of this to prevent internal double-bounces from bouncing
again. Whether that use is worthwhile or not is possible debatable.
--
Russ Allbery (rra(_at_)stanford(_dot_)edu)
<http://www.eyrie.org/~eagle/>